This invention relates to endocardial electrodes for electrical contact with an array of points on the inner wall of the heart of a living being. Such contact has long been recognized to be desirable for a number of purposes. One example is mapping of the muscle activation sequence of endocardial tissue. In this case, an array of electrodes is placed via a catheter within the left or right ventricle and, as the heart beats, a multichannel recorder simultaneously records respective electrograms of the sequence of potentials appearing at the individual electrodes. While this is occurring, the cardiologist seeks, by use of a fluoroscope, to determine the location of the various contact points of the electrodes with the ventricular wall, thus to correlate these locations with respective electrograms. If he is successful, he may find a point of initiation of heart arrythmia, which may then be treated. Early attempts of doing this were of limited value because of the few, and poor distribution of, points at which simultaneous readings could be taken.
Proposals have been made for achieving more contact points around the ventricle, such as by use of a compressible three-dimensional basket-like array of proximally and distally connected spring arms carrying electrodes, or by use of a series of free-ended, s-curved spring arms that spread distally, tulip-like, from a proximal connection point. Any attempt to implement such approaches encounters serious problems. One is the difficulty (even if some radio-opaque marking is employed) of fluoroscopically indentifying individual electrodes of such a more numerous, three-dimensional array within the heart to correlate the location of the many electrodes with respective electrograms; another is the difficulty of introducing such an elaborated assembly into the heart in a conventionally sized cardiac catheter, in a way that the assembly can spring into the desired distributed wall contact when released; another is the multiple opportunity for confusion of the cardiologist as he seeks to rapidly conduct this complex examination of the patient.
Because of such problems, the use of the three-dimensional, multi-electrode technique, though of considerable theoretical benefit, has not been acceptably implemented.
The present invention is direction to overcoming such problems, and to achieve practical use of a three-dimensional array of a large number of electrodes within a ventricle of the heart, comprised e.g. upwards of six or preferably considerably more electrodes.